The present invention relates to a method for storage area management included in a computer system having a storage subsystem that provides a thin provisioning volume. In particular, the invention relates to a technology of displaying information about the thin provisioning volume.
The storage subsystem provides a host computer with a logical unit (LU) by statically allocating a storage area of a physical disk. However, LU has the following disadvantages.
As one disadvantage, for example, the storage capacity of a physical disk allocated to the host computer is made larger than the storage capacity actually used by the host computer. This is because the storage capacity to be used by the application run on the host computer cannot be precisely grasped. As another disadvantage, the promotion cost taken in changing the capacity of the LU is high.
The thin provisioning technique has been known as a technology of overcoming these disadvantages. The storage subsystem provides the host computer with the volume (thin provisioning volume) realized by the thin provisioning technique.
This technology allows the storage subsystem to provide the host computer with the thin provisioning volume recognized as a volume having a larger storage capacity than the actually allocated storage capacity of a physical disk. In receipt of the request for write to the thin provisioning volume from the host computer, the storage subsystem dynamically allocates the storage area of the physical disk to the concerned thin provisioning volume to which data is requested to be written.
In some cases, however, the storage area of the physical disk may be wastefully allocated to the thin provisioning volume. For example, an application run on the host computer is executed to delete a file written on the thin provisioning volume. In this case, a difference takes place between the storage capacity of the physical disk allocated to the thin provisioning volume and the storage capacity used for the host computer. That is, the storage area of the physical disk is wastefully allocated to the thin provisioning volume.
Further, the thin provisioning volume is disadvantageous in performance of sequential access. The thin provisioning volume is inferior to the LU in the performance of sequential access. This is because the sequential addresses on the thin provisioning volume are not necessarily matched with the sequential addresses on the physical disk. Hence, the sequential access to the thin provisioning volume may be a random access to the physical disk. As such, as the sequential access is executed more frequently, the thin provisioning volume is inferior to the LU in access performance.
An administrator is required to determine which of the thin provisioning volume and the LU is to be used for storage promotion in consideration of merits and demerits of the thin provisioning volume.
In addition, the technology of aiding in the effective use of the physical disk allocated to the LU is disclosed in JP-A-2005-092308.